EP-A-0 51 351 disclose an Mg, Al mixed (hydr) oxide catalyst having an Mg:Al molar ratio above 3 and preferably in the range from 3-10.
The article of H. Schaper et al. in Applied Catalysis, 54, (1989) 79-90, discloses the same catalyst. This catalyst has a hydrotalcite structure, consisting of brucite type layers in which part of the bivalent ions (Mg) are replaced by trivalent ions, alternated by interlayers which contain water and anions to compensate for the excess charge of the trivalent ions. The preparation of such catalysts is disclosed. Due to the basic properties such catalysts are considered of special interest for base-catalyzed reactions, such as polymerization of propylene oxide, double-bond isomerizations of olefins such as 1-pentene, and aldol condensations. Exemplified is double-bond isomerization of 1-pentene using an Mg, Al mixed oxide catalyst having an Mg:Al molar ratio of 5 and 10. At increasing molar ratio the conversion rate decreases.
The article of Watanabe, Y. et al. in Microporous and Mesoporous Materials 22 (1998) 399-407, discloses the use of Mg—Al hydrotalcite catalysts having a molar ratio of 1.8-2.5 for the methanolysis of ethylene carbonate for the production of dimethyl carbonate.
EP-A-0,478,073 describes a process for preparing a dialkyl carbonate which comprises contacting an alkylene carbonate with an alkanol in the presence of a mixed metal oxide catalyst or a modified bimetallic or polymetallic catalyst under conditions effective to produce the dialkyl carbonate. In the examples, a magnesium/aluminium mixed metal oxide catalyst having a Mg:Al ratio of 3:1 was employed.
In JP-A-06/238165, a process is described wherein an alkylene carbonate and an alcohol are subjected to transesterification in presence of a catalyst to produce a dialkyl carbonate. A combination of Magnesium oxide and another metal oxide other than magnesium was used as catalyst in an atomic ratio in the range of 1000:1 to 20:1 of magnesium to the other metal.
The present invention has for its object to provide a method for the catalytic conversion of alkylene carbonate having an improved conversion rate and improved yield, while having limited leaching of metal from the catalyst.